Swift下标
示例
类，结构和枚举可以定义下标，这些下标是访问集合，列表或序列的成员元素的快捷方式。
例
struct DaysOfWeek {
var days = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
subscript(index: Int) -> String {
get {
return days[index]
}
set {
days[index] = newValue
}
}
}下标用法
var week = DaysOfWeek() //您可以通过array[index]在索引处访问数组的元素。 debugPrint(week[1]) debugPrint(week[0]) week[0] = "Sunday" debugPrint(week[0])
下标选项：
下标可以采用任意数量的输入参数，并且这些输入参数可以是任何类型。下标也可以返回任何类型。下标可以使用可变参数和可变参数，但不能使用输入输出参数或提供默认参数值。
示例
struct Food {
enum MealTime {
case Breakfast, Lunch, Dinner
}
var meals: [MealTime: String] = [:]
subscript (type: MealTime) -> String? {
get {
return meals[type]
}
set {
meals[type] = newValue
}
}
}用法
var diet = Food()
diet[.Breakfast] = "Scrambled Eggs"
diet[.Lunch] = "Rice"
debugPrint("I had \(diet[.Breakfast]) for breakfast")